Most people would agree that sex trafficking is abhorrent.

When a group of Senators proposed a new bipartisan bill called Stop Enabling Sex Traffickers Act it sounded like a noble piece of legislation that people would get behind. It would hold companies liable if they "knowingly facilitate" sex trafficking on their online platforms. But tech industry associations and internet-rights advocates are concerned about protections of free-speech platforms.

The bill, introduced on Tuesday, comes after a two-year Senate investigation into online sex trafficking on the classified ads site Backpage.com. The investigation, led by bill co-sponsors Senators Rob Portman and Claire McCaskill, found that Backpage.com knowingly aided criminal sex trafficking of women and young girls, simply scrubbing terms from ads such as "Lolita," "teenage," "rape," "amber alert," and publishing them on its site. After the investigation was published in January, Backpage.com shut down its adult ads section.

Backpage.com has been targeted with several lawsuits over the years, but has been largely protected by Section 230 of the 1996 Communications Decency Act, a legal protection that gives a broad layer of immunity to online companies from being held liable for user-generated content. Companies are supposed to act in good faith to protect users but critics argue it can be used as a shield. (It doesn't, however, protect sites from federal liability against criminal law, like child-pornography laws.)

The bill seeks to clarify Section 230 to "eliminate federal liability protections for websites that assist, support, or facilitate a violation of federal sex trafficking laws." In addition, the new law would "enable state law enforcement officials, not just the federal Department of Justice, to take action against individuals or businesses that violate federal sex trafficking laws."

"The Communications Decency Act is a well-intentioned law, but it was never intended to help protect sex traffickers who prey on the most innocent and vulnerable among us," said Portman in a statement about the new Senate bill, which is aimed to hold Backpage.com's feet the fire, among other companies. A similar bill was introduced in the House in April, which suggests clarification to the CDA, as well as fines or up to 20 years imprisonment for companies who illustrate "reckless disregard" for content posted on their platforms.

Aaron Mackey, a Frank Stanton legal fellow at the Electronic Frontier Foundation, says the efforts could be cause for worry.

"This bill can return us back to a time before Section 230 was passed in which platforms will be increasingly liable for content posted by third parties that they may not know about," Mackey said. He added while the Googles and Facebooks of the world are armed with legal teams that can help them battle any flood of lawsuits, it's more concerning for smaller companies with more limited resources.

The battle is heating up: On Wednesday, 10 tech trade groups including the Internet Association, Interactive Advertising Bureau, and Computer and Communications Industry Association coauthored a letter condemning the bill. They wrote that the carve-out would have "significant unintended consequences," stating that it creates legal ambiguity the amendment that would have a "chilling effect."

"Platforms will err on the side of extreme caution in removing content uploaded by their users, while cutting back on proactive prevention measures," they wrote.

Consumer Technology Association echoed these sentiments in a separate letter on Wednesday. The CTA suggested that bad actors "could easily escape by changing their URL address or relocating abroad" whereas legitimate tech companies will bear the burden of costly and time-consuming lawsuits.

"We urge Congress to take a narrow approach that directly targets bad actors,' the CTA continued. "Specifically, Congress should urge the Department of Justice to aggressively use its powers to identify and prosecute the limited number of rogue websites that are violating the law." In July, five members of Congress asked Attorney General Jeff Sessions to launch a criminal probe into Backpage.com's role in human trafficking.

On Wednesday, Portman and bill cosponsor Senator Richard Blumenthal responded to what they called "false claims" of tech association groups. "It is narrowly-crafted legislation that targets websites engaged in one criminal activity: sex trafficking. And it allows victims of sex trafficking to impose civil remedies and seek justice," they said in a statement. "The courts have said Congress must act to fix this problem, and Congress has a responsibility to ensure justice and stop these heinous crimes."